There has been extensive research into the link between stress and the immune system that shows that the link is indeed very strong with a positive correlation. The research is seen in the general adaptation syndrome, Stone's experiment on stressful events and the links to symptoms, Cohen et al experiment on the common cold, and Keicolt Glaser who looked into immune function.
Stress has been found to suppress the immune system allowing people to contract disease far faster than a person with less or no stress within their lives.
The General Adaptation Syndrome (GAS) was carried out by Selye who put rats under enormous stress to assess their responses. The stressors they were exposed to were bacterial infection, toxins, physical restraint and extreme heat and cold. He called their overall reaction the GAS. There are three stages of GAS, Alarm Reaction Stage, Resistance Stage, and Exhaustion Stage. The Alarm reaction stage makes the ANS respond to the stressor.
The Resistance Stage is when all alarm systems are a full capacity so the parasympathetic nervous system calls for a more cautious use of resources. Coping strategies such as denial are used and the "fight or flight" response is less effective. When the stress reduces there is a period of adjustment. The Exhaustion Stage is when, eventually the physiological systems in the previous stages become ineffective and the initial ANS symptoms of arousal reappear. In extreme cases, attempts to return to a normal state fail, and the final stage occurs.
The positive evaluation of Selye's work is that the work started the study of understanding stress. It has been useful in predicting physiological responses to stress. The GAS provides a very useful model of the course of physical injuries and illness in cases where stress is prolonged.
The negative evaluation of...